As email servers filtering technique are getting more and more effective, mass or bulk email marketers are resorting to hijacking ordinary PCs by installing "worms or Trojans with built-in SMTP engine" called "Proxy-Guzu or Jeem" to spam without the owner knowledge.

Free anti-spam zombies, spambot, spyware, adsware software program (below).

When an unwitting user execute these "Trojans" on their PCs--the Trojan listens on a randomly-chosen port and using its built-in mail client to dash off a message, ie; to a Yahoomail account together with the victim computer port number and IP address in the subject line.

The spammers uses the information and relay as much email as they can through the captured computer, knowing that mails being traced will lead to the hijacked Internet Address.

Viruses, Spyware, and Mailicous Code
Not too long ago viruses and spyware started to appear, some disguise as freeware that transparently load themselves or are sent via email to your mail client (ie: outlook, eudoramail, etc.).

And these spyware--"report" and send your address book contact lists back to their home base, some examples:

Proxy-Guzu or Jeem spam zombies Trojans that hijack ordinary PCs without the owner knowledge by installing built-in SMTP engine program to send spam.

The Klez virus for example, select random email address from an infected PCs and insert the email address into the "From:" and "To:" fields, making it appear that someone else has sent the message.

The W32.Yaha.P@mm worm/virus that email itself to all of the contacts in your Windows Address Book, MSN Messenger, .NET Messenger, Yahoo Pager, and in all the files whose extensions contain the letters HT.